The present invention relates to a method of disposing of a waste fiber reinforced aluminum alloy composites. More particularly, the present invention is concerned with a method of disposing of a fiber reinforced aluminum alloy composite by which inorganic short fibers contained in the composite can be discarded after being transformed into a form which is harmless to the human body.
In recent years, a metal composite reinforced with an inorganic short fiber is being put to practical use as a highly functional composite. Especially, the availability for a wide variety of applications is being expected on the fiber reinforced aluminum alloy composite comprising an aluminum alloy as a matrix and an inorganic short fiber as a reinforcement, because the composite exhibits performances derived from a composite structure which is characterized by a combination of a light weight with markedly high strength, rigidity, flexibility, etc. In such a fiber reinforced aluminum alloy composite, ceramic whiskers composed of fine acicular single crystals of SiC, Si.sub.3 N.sub.4, Al.sub.2 O.sub.3, ZnO or the like or chopped fibers obtained by chopping long fibers of SiC, Al.sub.2 O.sub.3, SiO.sub.2 or the like are used as the inorganic short fiber, which are generally composited with an aluminum alloy as a matrix by powder metallurgy or squeeze casting.
Recently, however, it has been pointed out that such an inorganic fiber, especially a whisker having a fine acicular fiber form, is likely to reside in the lump when inhaled in a human respiratory system, thereby causing health damages. Hence, safety measures are under study during the manufacture of the inorganic short fiber and handling thereof in bulk (powder). However, no study is in progress on the disposal of wastes, such as process scraps and return scraps of the composite generated in the step of manufacturing the composite and spent parts generated in the stage of practical use.
These wastes do not cause any damage to the human body by flying about, unlike other wastes in bulk (powder) form, because the inorganic short fiber is dispersed and carried in the texture of the aluminum alloy matrix. However, the discarding of these wastes as such is not desirable from the viewpoint of health problems, because SiC whiskers are extremely stable and will fly about, though the aluminum alloy will be corroded.
A possible countermeasure therefor comprises dissolving the wastes for recycle. However, when the wastes are redissolved, the whiskers form agglomerates and thus fail to effect a uniform dispersion in the matrix. Hence such redissolution is a less feasible measure at present.